Agent of Byzantium is a collection of short stories by Harry Turtledove, centred on the exploits of Basil Argyros, a Byzantine secret agent. The stories are set in an alternate 14th century, where Islam never existed and the great ancient empires of Byzantium (the Eastern Roman Empire) and Sassanid Persia survive.

Here, collected and somewhat rearranged into novel form, are Turtledove's stories (1985-87) about Basil Argyros, a ""magistrianos"" (secret agent) of an alternate Byzantine Empire that never fell (one reason was that the Prophet Mohammed never founded Islam; instead, he converted to Christianity and eventually became a saint). So now, in the early 14th century, Byzantium's only rival is Persia. Basil's a sort of Byzantine Batman, so his adventures cover a lot of territory. He feigns desertion to join up with some invading nomads and steals the telescope the nomads have just invented. During a smallpox epidemic (his wife and child die), he discovers the immunizing ability of cowpox. He wrests the secret of making gunpowder away from a remote, rebellious band of monks. He thwarts a Persian-inspired attempt to stir up religious strife by means of inflammatory broadsheets, and so discovers the power of the printing press--but the guilty party, lovely Persian superspy Mirrane, evades capture. Finally, Basil unveils his latest secret weapon--whiskey--and teams up with Mirrane to defeat an invading Khirgiz horde that threatens both Byzantium and Persia. The backdrop is intriguing but Basil and his adventures are hard to believe in, and the whole enterprise breezes pleasantly along without coming fully alive. Thus far, then, IAP has opted for what is no better than the safe and mediocre.